STM32H747I-DISCO LCD DISPLAY PROBLEM

[vanisrinivasulu]

Split from: https://community.st.com/t5/stm32-mcus-boards-and-hardware/stm32h747i-disco-lcd-display-problem/td-p/643493

Hello, 

May ,I know how to enable the display. I am not getting how to on the backlight of the display 

[vanisrinivasulu]

I was given 5Vsupply to the card using the micro b usb cable and the stm32 board getting 5v .still my display is not enabling ...even with firmware part also i was tried taking the PJ12 Pin (used for BL_CTRL)  taking as output . 

[Sco]

To debug backlight:

First step, please check the "+5V" power is provided well: to probe C3 or C76 on the MB1248.

Second step, if the first step ok: 5V provided well on the MB1248, then to check if on the LCD board(MB1166), whether it gets the 5V well. To probe the C3 or C4 or C5.

Third step, to check if the LCD board gets the 5V well, then to check if the output is good or not, to probe C1 or C2 on the MB1166. Also you can measure the the Vfb(Probe R3 on the MB1166).

[vanisrinivasulu]

Step 1:
I checked the capacitor C3, and one end is getting 4.92V while the other end is 0V. Similarly, C76 has 4.89V on one end and 0V on the other end.

Step 2:
The MB1248 LCD board is receiving 5V. I checked the capacitors C3, C4, and C5 as suggested. All three capacitors are showing 0V. According to the schematic, one side should have 0V, and the other side should have 5V. However, when I measured, it showed 0V on both sides.

Step 3:
The same issue occurs with capacitors C1 and C2, as both are showing 0V.
What should I do now?

The below are the Schematic diagrams .please check the below schematics

[Sco]

From the data you provided, the power supply failed(step2).

one possibility: the connection between MB1166 and MB1248 is not good, or L1(On MB1166) is damaged, then in "C3, C4, C5" side you can detect the 5V voltage.